Aarskog syndrome 10/29/2013
Facial-digital-genital syndrome Causes: Aarskog syndrome is a genetic disorder that is linked to the X chromosome. It affects mainly males, but females may have a milder form. The condition is caused by changes (mutations) in a gene called "faciogenital dysplasia" ( FGD1 ).

Aase syndrome 09/08/2013
Aase-Smith syndrome; Hypoplastic anemia/Triphalangeal thumb syndrome Causes: Most cases of Aase syndrome occur without a known reason and are not passed down through families (inherited). However, some cases have been shown to be inherited. This condition is similar to Diamond-Blackfan anemia, and the two conditions should not be separated.

Abdominal aortic aneurysm 08/13/2013
Aneurysm - aortic; AAA Causes: The exact cause of the condition is unknown. Factors that can increase your risk of developing the problem include: Smoking High blood pressure Male gender Genetic factors An abdominal aortic aneurysm is most often seen in males over age 60 who have one or more risk factors.

ABO incompatibility 05/29/2014
A, B, AB, and O are the four major blood types. The types are based on small substances (molecules) on the surface of the blood cells. When people who have one blood type receive blood from someone with a different blood type, it may cause their immune system to react. This is called ABO incompatibility. Causes: The different blood types are: Type A Type B Type AB Type O People who have one blood type may form proteins (antibodies) that cause their immune system to react against one or more of the other blood types.

Abscess 08/31/2014
An abscess is a collection of pus in any part of the body that, in most cases, causes swelling and inflammation around it. Causes: Abscesses occur when an area of tissue becomes infected and the body's immune system tries to fight it. White blood cells move through the walls of the blood vessels into the area of the infection and collect in the damaged tissue. During this process, pus forms. Pus is the buildup of fluid, living and dead white blood cells, dead tissue, and bacteria or other foreign substances.

Absence seizure 02/20/2014
Seizure - petit mal; Seizure - absence; Petit mal seizure; Epilepsy - absence seizure Causes: Absence seizure occur most often in people under age 20, usually in children ages 6 to 12. They may occur with other types of seizures, such as generalized tonic-clonic seizures (grand mal seizures), twitches or jerks (myoclonus), or sudden loss of muscle strength (atonic seizures).

Absent pulmonary valve 02/17/2014
Absent pulmonary valve syndrome; Congenital absence of the pulmonary valve; Pulmonary valve agenesis Causes: Absent pulmonary valve occurs when the pulmonary valve does not form or develop properly while the baby is in the mother's womb.

Achalasia 02/10/2014
Esophageal achalasia Causes: There is a muscular ring at the point where the esophagus and stomach meet, called the lower esophageal sphincter. Normally, this muscle relaxes when you swallow. In people with achalasia, it does not relax as well. In addition, the normal muscle activity of the esophagus (peristalsis) is reduced.

Achilles tendinitis 08/11/2012
Tendinitis of the heel Causes: There are two large muscles in the calf. These muscles are important for walking. They create the power needed to push off with the foot or go up on the toes. The large Achilles tendon connects these muscles to the heel.

Achondrogenesis 08/22/2013
Achondrogenesis is a rare type of growth hormone deficiency in which there is a defect in the development of bone and cartilage. Causes: Achondrogenesis is inherited, which means it is passed down through families. Some types are known to be recessive, meaning both parents carry the defective gene and the chance for a subsequent child to be affected is about 25%. Symptoms: Very short trunk, arms, legs, and neck Head appears large in relation to the trunk Small lower jaw Narrow chest Exams and Tests: X-rays show bone problems associated with the condition.